#include <stdio.h>
#include <gsl/gsl_sf_bessel.h>

//extern "C" double gsl_sf_bessel_J0(const double x);

int
	main (void)
{
	double x = 5.0;
	double y = gsl_sf_bessel_J0 (x);
	printf ("J0(%g) = %.18e\n", x, y);
	return 0;
}